Identify and construct the identity matrix

\[\begin{bmatrix} 0 & 1 \\ 1 & 0 \end{bmatrix}\]

\[\begin{bmatrix} 1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{bmatrix}\]

\[\begin{bmatrix} 0 & 0 \\ 0 & 0 \end{bmatrix}\]

\[\begin{bmatrix} 1 & 1 \\ 1 & 1 \end{bmatrix}\]

\[\begin{bmatrix} 1 & 0 \\ 0 & 1 \end{bmatrix}\]